Why different boil times?

[Flatheadfever]

I have been doing the Noble grape kits and it has 20 minutes steep time and a 30 minutes boil time with their kits.
I read that some recipes have 60 minute boils. Why is that and can you change the length of the boil for any kit?
I want to start experimenting with recipes.
Lindsay

[LiverDance]

Not sure how the NG kits are calculated but a standard boil time is 60 to allow you to get the most from your hops. You should ask the people at NG next time you in or give them a call. I remember doing kits and boiling them for 60 mins. here is a great online resourse that may answer some questions http://www.howtobrew.com/intro.html" onclick="window.open(this.href);return false;

[chalmers]

Experiment away, I say!
The most popular boil times in recipes are 60 minutes, as this gives sufficient time to have an early, middle and late hop additions. Hopping your wort is one of the major reasons to do a boil, and depending on when in the boil you add them, they will impart primarily bitterness, flavour, or aroma (same order as above). You can do no-boil beer, as well as quite long boils (Dogfish Head 120min IPA), but most all-grain homebrewers are in the 60-90min range.
You can definitely change the length of your boil for any recipe, but keep in mind that some extract will darken the longer it is in the boil (caramlization, etc), so your pilsner might turn out black. But it'll probably taste great.

http://beer.about.com/od/wortcooling/a/boil.htm" onclick="window.open(this.href);return false;

[amartin]

I remember they explained it to me once as being because they're extract kits, so the extract has already been boiled and just needs to be diluted to be made into wort. However, it still needs a boil for hopping. They didn't say it, but I suspect that they went with a shorter boil because while it means needing more hops, a new brewer might prefer the time savings and still be impressed by the low cost compared to what they'd pay at the NSLC. They're trying to make this as easy as possible for them.

[sleepyjamie]

my guess is when people switch from festa brew to extract they want to make the process as easy as possible so 30 minute boils are likely to attract more customers than 60 minute.

[jason.loxton]

30 minute boils also allow for smaller pots (less evaporation), and so may be easier for those getting started that lack equipment.

[benwedge]

One thing to keep in mind is that the extract affects the ability of the water to absorb the hops' flavour. You're working with a smaller amount of water and but as much sugar as a full boil. On my extract brews I added the extract in the final 15 just to make sure any living things were killed, and that helped avoid fears of caramelization.